Recently, a variety of types of optical discs have been proposed as a recording medium that can be removed from a recording apparatus. These recordable optical discs have been proposed as a large capacity medium of several GBs and are thought to be promising as a medium for recording AV (audio visual) signals,
Among the sources (supply sources) of digital AV signals, recorded on the recordable optical disc, there are, for example, a bitstream the recording apparatus itself forms on picture compression of analog input audio video signals in accordance with the MPEG-2 system, and a bitstream of the MPEG-2 system, directly obtained from electrical waves of digital television broadcast. In general, an MPEG-2 transport stream is used in digital television broadcast. A transport stream is composed of plural concatenated transport packets. Each transport packet is a packetized MPEG-2 video stream or MPEG-1 audio stream, with the data length of each transport packet being 188 bytes in length. If an AV program of a transport stream, received over digital television broadcast, is directly recorded on an optical disc by a recorder, recording can be made without deteriorating the video or audio quality whatsoever.
In order to permit a user to search a scene of interest, such as a program locating point, in the transport stream recorded on the optical disc, it is required to be able to perform random-access reproduction.
In general, in an MPEG-2 video stream, I-pictures are encoded at an interval of 0.5 sec, whilst other pictures are encoded as P- or B-pictures. Thus, in reproducing the video by random-accessing a transport stream recorded on the optical disc, I-pictures must be searched first.
However, if a transport stream, recorded on the optical disc, is random-accessed for video reproduction, it is difficult to search the starting byte of an I-picture efficiently. That is, the syntax of the video stream needs to be analyzed from a random byte position of a transport stream on the optical disc to search the start byte of the I-picture. So, the I-picture searching is extremely time-consuming, such that it is difficult to perform random-access reproduction with quick response to the user input.